1985 OMC 65, 100 and 155 HP Models Commercial Service Manual, PN 507450-D, Page 356Get this manual
Checking the RectifierRegulator Assembly Charging System35 Amp with Variable Load High Rate Discharge Tester
Test must be performed with variable load high rate discharge tester (carbon pile) capable of drawing at least 35 amps1Disconnect the battery cables at the battery2Connect zero to forty (0 to 40) ammeter between the rectifierregulator assembly red lead and the starter solenoid3 Reconnect the battery cables4Connect variable load tester (carbon pile) across the battery terminals5With the variable load tester, draw about 30 amps from the batteryStart and run the engine to approximately 3000 rpmThe ammeter should indicate approximately 30 to 35 amps output6Decrease the variable load tester from 30 to ampsThe ammeter will begin to show decrease in current outputAs the current decreases, the voltage across the battery should stabilize (regulate) at 14 to 15 voltsIf the ammeter does not indicate as described in the above test, the stator should be checked first